Title

Author

Honors Program

University Honors

Date of Award

5-2016

Thesis Professor(s)

Rebecca A. Pyles

Thesis Professor Department

Biological Sciences

Thesis Reader(s)

James R. Stewart, Tom W. Ecay

Abstract

In squamate reptiles, the evolutionary transition from oviparity to viviparity is accompanied by loss of the calcareous outer eggshell, which suggests significant implications for the role of calcium during embryonic development (Packard et al., 1977). An experiment was designed to evaluate the impact of reduced calcium availability during development in the oviparous corn snake, Pantherophis guttatus (Stewart and Ecay, 2013). Results from that study showed significant decreases in the mass and length of hatchling corn snakes when the outer calcareous eggshell layer was removed during development. In vertebrates, variation in total body length reflects skeletal differences---primarily differences in the number or sizes of vertebrae and/or differences in length of the skull. Skeletal components obviously are affected by the availability of calcium during development. My study was designed to determine the anatomical and developmental bases for the smaller size observed in hatchling snakes subjected to reduction of eggshell calcium during embryonic development.

My hypotheses were, as follows: 1) Differences in mass reflected differences in overall length of hatchlings; 2) Differences in length resulted from decreased size of vertebrae---rather than decreased number---and/or decreased length of skulls in hatchlings with reduced calcium. Hatchlings were prepared for skeletal analysis via clearing-and-staining. Vertebrae of each hatchling were counted and size measurements obtained for separate spinal regions (cervical, thoracic, and caudal). Results demonstrate a significant treatment effect on size of vertebrae in the thoracic and anterior caudal regions, as well as length of the skull. These findings suggest that reduced developmental calcium, comparable to the condition in viviparous species, impacts ossification and growth of skeletal elements in late development.